The present invention is directed to apparatuses and methods for non-destructive inspection, and more particularly, to automated real-time, non-destructive inspection apparatuses and methods.
Real-time x-ray machines for detecting flaws or defects in metallic structures are known. A real-time x-ray machine can provide a continuous x-ray image of a structure moving across the x-ray machine""s field of view. Conventional real-time x-ray machines are typically based on cartesian motion control systems that allow translational movement of an x-ray source and imaging panel in one or two degrees of freedom relative to the stationary structure being inspected. Such systems are inherently limited in flexibility, and often cannot adequately image all desired areas of complex structures without repositioning of the structures relative to the x-ray source. For large or awkward structures, this repositioning to ensure accurate imaging may prove time consuming and labor intensive. In addition, this repositioning may also require expensive fixturing or heavy-duty motion systems, with different structures requiring different item-specific fixtures.
To maintain the integrity of the resulting x-ray image, conventional x-ray systems typically require that the plane of the imaging panel be perpendicular to, and at least approximately centered on, the x-ray beam axis. Significant problems or difficulties may be encountered if the x-ray source and imaging panel are allowed to move independent of each other off the x-ray beam axis. As one solution to this problem, Xylon Corporation produces a real-time x-ray system having a rigid C-frame that holds the x-ray source and imaging panel in a fixed relationship to each other during motion to ensure proper imaging. The C-frame, however, is only free to translate in two degrees of freedom relative to the part, and thus repositioning of structures is often required for comprehensive x-ray inspections.
When an acceptable flaw or defect is found in a structure through x-ray inspection, it is important to identify the actual location of the defect on the structure so that a subsequent inspection or repair can be effectively carried out. One difficulty with conventional real-time x-ray systems is that the axial location of the defect along the x-ray beam axis may be difficult to ascertain for structures having substantial depth or multiple portions along that axis. For example, when inspecting a circumferential weld around a cylindrical duct where the x-ray beam axis is positioned parallel to the weld plane, it may be difficult to determine if an observed defect in the weld exists on the near side of the duct or the far side of the duct relative to the x-ray source. If the axial location of the defect cannot be sufficiently determined, then either the x-ray machine or the structure must be repositioned for further x-ray imaging in an effort to ascertain the defect""s actual location.
The size of defects in metallic parts is often extremely small and non-visible to the human eye. In addition, the lack of reference points on the surface of a structure often make it difficult to correlate the location of a defect as seen on the x-ray image display screen to a precise location on the part. For these reasons, it may be difficult to determine the precise lateral location of a defect on the surface of a part, even when the general axial location of the defect can be ascertained.
By placing a structure for inspection between the x-ray source and the imaging panel, any defect observed will be projected onto the imaging panel in a magnified size. Another difficulty with conventional real-time x-ray systems is that even when the axial and lateral location of the defect can be ascertained, the actual size of the defect is often difficult to determine with any precision because of this geometric magnification. Determining the size of the defect is important, however, as it will dictate either the acceptability of the structure or the nature of the repair which must be carried out. Determination of the defect""s size in conventional systems, however, has typically required physical measurements by an operator using manual measuring devices. Not only is this a tedious, labor intensive exercise, but it can also result in a somewhat inexact determination of the size of the defect.
The present invention provides a real-time, non-destructive inspection system usable to inspect a selected structure for defects. The inspection system is also usable to visually identify a defects location on the structure. One embodiment of the invention provides an articulatable robot arm movable relative to the structure. A movable support system is attached to the articulatable robot arm and has first and second support portions spaced apart from each other defining a space therebetween sized to receive the structure being inspected. An imaging source is attached to the first support portion and is adapted to project an imaging beam along an imaging beam axis. An imaging detector panel is attached to the second support portion and is spaced apart from the imaging source. The imaging detector panel is positioned at least approximately perpendicular to, and intersecting, the imaging beam axis. The imaging source and detector panel are configured to provide images of the structure. A display screen is coupled to the imaging detector panel to display the images of the structure in real-time as the structure is being inspected. Accordingly, the inspection system of the present invention can fully inspect the selected structure by maneuvering the imaging source and imaging detector panel relative to the structure while providing images of the structure to the operator in real-time.
Another embodiment of the invention includes a visual targeting system adjacent to the imaging source and configured to identify where the imaging beam axis intersects the structure undergoing inspection. The visual targeting system in one embodiment has a first line generator positioned adjacent to the imaging source and configured to project a first light plane collinear with the imaging beam axis. A second line generator is also adjacent to the imaging source and configured to project a second light plane collinear with the imaging beam axis and non-parallel to the first light plane. The intersection of the first and second light planes is collinear with the imaging beam axis. In the one embodiment, the intersecting light planes create illuminated cross-hairs that visually indicate the imaging beam axis location on the selected structure to facilitate finding a defect""s location on the structure.
Yet another embodiment of the invention provides a method for determining the size of a defect in the selected structure by determining a distance between the imaging source and the defect. The method comprises providing the imaging source in a first source position with an image of the defect on the detector panel being in a first image position. An axial distance between the imaging source and the imaging detector panel is determined when the imaging source is in this first source position. The imaging source is moved to a second source position with the image of the defect on the detector panel being moved laterally to a second image position. The distance moved by the imaging source between the first and second source positions, and the corresponding distance moved by the image of the defect on the detector panel between the first and second image positions, is determined. The distance between the imaging source and the defect is then determined based on the distance between the imaging source and the imaging detector panel, the distance moved by the imaging source, and the corresponding distance moved by the image of the defect. To determine the actual size of the defect, the magnification of the defect""s image is determined by the ratio of the distance between the imaging source and the imaging detector panel to the distance between the imaging source and the defect. Accordingly, the size of the defect is then determined by dividing the defect""s image size by the magnification of the defect""s image.